In many commercial motor applications, for example computer fans, there is a need to reduce size and cost of the motor and motor system. However, while reducing the size and cost of the motor and motor system, an increase in motor torque is often desirable. For example, in the above computer fan application, the size and cost of the overall computers are decreasing, thus creating a need to reduce the size and cost of the applicable fan motors and fan motor systems. In addition, a reduction in size of the computer combined with an increase in computational performance typically means that more heat is internally generated inside the computer. For product reliability purposes, this increased heat may need to be removed from the product. The need to remove more heat may require a fan motor that generates greater torque while, at the same time, reducing the size and cost of the fan motor and fan motor system.
In one prior art application, a 1-coil or a 2-coil winding motor is used to provide low cost and low complexity. But as more torque may be required (due to increased heat removal requirements), the 1-coil or 2 coil winding motor may have limited efficiency and torque output. Multiphase motors may be more efficient and provide greater torque due to the reduced percentage of the low or no torque angles of rotation.
A multiphase motor control may utilize three sensors that may need to be accurately placed at precise locations at predefined distances apart from each other. These three sensors (that are located at different locations) detect rotor angular motion at different times (due to their respective different placement locations). This allows the system to distinguish each phase in the motor stator. This multiphase motor control may require precision assembly methods to properly locate three sensors and also the additional equipment cost of the three sensors.
Another type of multiphase motor control has one sensor but may also require a more complex rotor. This rotor includes physical coding or marking to distinguish between each stator phase. This more complex rotor may involve more material and assembly costs.
There is also a method for multiphase motor control called ‘sensorless’ control. This method typically involves monitoring the BEMF voltages of the motor stator windings, which are then used to interpolate phase location. This method does not involve the cost of any sensors, but may require complex, precision analog-type circuitry. Therefore, this ‘sensorless’ method may require the cost of the complex circuits and the cost associated with the time required to test and validate these complex circuits.
Accordingly, a need exists for a device, method, and system that provides less complex circuitry and easier implementation in a variety of applications and, therefore, is typically more cost effective. In addition, the device, method and system may only require the cost of one sensor and may not require the precision assembly and location of multiple sensors. In addition, the device, method and system may not require any physical coding or marking (other than the standard rotor magnetic pole-pairs) to distinguish each stator phase and, therefore, does not require the material and/or cost that the more complex rotor may incur. In addition, the device method and system may reduce the cost of multiphase motors so as to allow them to become more commercially feasible in applications that previously were only commercially feasible as 1-coil or 2-coil motors.